Allergies Diagnosis

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It's important to pinpoint exactly what's sparking your allergy symptoms in the first place. Even if you think you know, it's good to check again down the road because allergies to new substances can develop. Allergy testing from a board-certified allergist or immunologist should take place if you find your symptoms are not being adequately controlled. Allergy tests are practically painless, and because they're more accurate than they used to be, they may actually detect precisely what's causing your allergy symptoms, which in turn will help your doctor tailor an effective treatment plan that works for you. Simple tests like the skin-prick test can help uncover allergies to many common substances, including dust mites, pet dander, mold and pollen.

To diagnose allergies, a healthcare provider may ask the following questions:

Do allergies run in the family? If so, which relatives have them, and what are they allergic to?

Do symptoms recur at certain times of the year or are symptoms present year-round?

Does being around pets trigger symptoms in the eyes, nose or chest?

Do eating certain foods cause symptoms to flare?

How long do symptoms last?

What seems to make symptoms worse? What makes them better?

Have any medications to alleviate symptoms been tried? Were they successful or not?

Are any over-the-counter or prescription medications being taken? If so, which ones? (It's often helpful to take medications to the appointment.)

Are medications being used as prescribed by a healthcare provider?

Are there any medication allergies?

A healthcare provider should examine the nasal mucous membranes, as well as eyes, ears, mouth and throat. Nasal membranes may appear swollen and pale or bluish.

Allergy specialists use skin tests to determine the specific allergens that may be responsible for allergies. He or she will inject diluted extracts from allergens -- particular foods, pollens, dust mites, etc. -- under the skin or into a tiny scratch or puncture on the arm or back. With a positive reaction, a raised, reddened area with a surrounding flush will appear at the test site, indicating antibodies to that specific allergen are present in the skin. Prick tests are done first; an intradermal test may also be required.

The healthcare provider might also do a blood test, which is not as sensitive as a skin test. Using a sample of blood, the test looks for levels of antibodies to particular allergens.

If the healthcare provider suspects a food allergy, he or she may try an elimination diet, but only if reactions are not severe. This technique involves not eating any of the suspected trigger foods for a week or two to see if symptoms go away, then returning the foods to the diet over several days to see if the symptoms appear.

The three main causes of allergy symptoms are allergic rhinitis, irritant rhinitis or a combination of both (called mixed rhinitis). Allergic rhinitis is caused by a component of your immune system called the immunoglobin E (IgE) antibody. The cause of nonallergic rhinitis or irritant rhinitis s is a direct irritation of your nose. There is no way to tell them apart by just asking questions, not even for an allergist.

Allergy testing (either skin test or blood test) determines which of these is the underlying cause of your allergy symptoms. Allergic rhinitis is an immune system response that has positive allergy tests (either scratch test or blood test). Irritant rhinitis is a nonimmune response that has negative (normal) allergy tests.

It's important to know what causes your symptoms, because the right diagnosis will lead to the right treatment.

To diagnose your seasonal allergies, including whether -- and which -- allergens may be causing your symptoms, your doctor may order one or more of the following tests:

Skin Prick or Puncture Test -- A skin prick test is a simple allergy testing procedure in which a number of allergens (in droplets) are placed on the skin -- usually on the forearm, upper arm, or back. The skin is then gently pricked, which allows the allergens to get into the skin cells. If this produces an allergic response -- temporary redness, swelling and itching at the test spot -- it means you're sensitive to that allergen. And the greater the reaction, the more likely it is that you're not only sensitive to it but also allergic to it. Reactions to skin prick allergy tests usually appear fairly quickly, within 15-20 minutes. But it's also possible to have a delayed reaction several hours later. If this happens, notify your doctor or nurse.

Intradermal Test -- This test is similar to a skin prick test, but the allergens are injected under the skin using a syringe and a much more dilute solution. The intradermal allergy testing procedure is typically used when results from skin prick tests are unclear or if repeated tests have not triggered a reaction to any allergens.

Antibody Blood Test (RAST) -- A RAST (radioallergosorbent) blood test looks for specific immunoglobulin E (IgE) antibodies in your blood. If the antibodies are present, it most likely indicates a true allergic reaction. RAST is the safest type of allergy test, but compared with a skin prick test, it takes longer to produce results and it can't test for as many allergens at once.

This type of allergy test is typically used only in special circumstances where skin testing is not advised -- for example, if a person has a severe skin condition or is taking certain medications. Ask your doctor about the risks versus the benefits of both the skin prick test and the RAST blood test.

Skin allergies and their triggers are most commonly diagnosed through skin tests, including scratch tests, prick tests, and most commonly patch tests. Skin testing usually involves a doctor applying samples of allergens to a small area of skin, usually on the forearm, and then sometimes scratching or pricking the skin to let the allergen seep in. After some time, usually anywhere from 15 minutes to 96 hours, the doctor examines the skin to determine whether there was a reaction to the substance. If a person has certain skin conditions or is taking medications that would interfere with a skin test, a blood test that analyzes levels of antibodies may be done instead.

If you already know what is causing your rash, say a new soap or the ring you bought on the street that contains nickel, you can do things to avoid it so your rash doesn’t come back. But for those who have no idea what’s causing their reaction, an allergist can perform a patch test to (hopefully) isolate the pesky allergen that is causing your discomfort. There are two techniques:

1) A drop of a liquid containing the suspected allergen is dropped onto the skin (usually on your arm or back, depends on how many you’re testing). Your doc will then prick the area. If the skin turns red and blotchy, that indicates the possible presence of an allergy. Possible is key here; skin tests do yield many false positives.

2) A small amount of the potential allergen is injected under the skin. If a lump appears at the site of the injection, you are judged to have tested positive. The bigger the lump, the stronger the liability.

And don’t worry, these unpleasant red bumps aren’t permanent. They’ll heal and disappear about a week after the test. There is a controversy over how valid this type of testing is.

A general practitioner can read diagnostic lab reports showing, say, that a patient has allergic antibodies to pollen and nuts, but not to cat dander, or any number of other combinations. However, the bigger question is whether the tests conflict with or support the patient's history, or whether the expense and time involved could have been avoided just by listening to the patient with a trained ear. The science is there, but you don't have to look at all the molecules every time.

Science shows us that skin tests and blood tests for allergies don't really measure the same things. The antibodies that register in a blood test have a half-life of two days. They come and go without putting your immune system on a state of red alert. The ones that react in the skin have a half-life of six to eight weeks, which means that your body is ready to strike for a protracted period.

The delayed hypersensitivity (TB or candida skin tests) test is a descendant of the old tine test, and utilizes either the familiar PPD tuberculin, or candida, mumps, or other substances that most people have been exposed to at one time in their lives. The process involves injecting a few drops under the skin, usually on the forearm. The physician observes the site in 72 hours for a reaction. In a normally functioning immune system, the candida or mumps sites should show a raised, red area. This test is also qualitative as it determines the function of the T cell or cell-mediated system.